It was no surprise that President Obama headlined a big pro-union Labor Day rally in Milwaukee — giving a predictable speech in which Obama boasted about the country’s “economic gains” under his leadership.

What could well be surprising to many, though, was a conspicuous absence from the stage on which Obama fired up the pro-labor crowd.

Wisconsin, while a big union state with a passionate Democrat base, has a high-profile Republican governor in Scott Walker — a governor who survived a hard-fought recall effort sparked by Walker’s curtailing of public-employee union collective-bargaining rights — a governor who now faces a tough re-election battle.

Walker’s opponent in the governor’s race is Mary Burke, a former executive at the Trek Bicycle Corporation who is widely supported by Democrats hoping to knock off Walker. So, you might think that Burke would jump at the opportunity to appear alongside the country’s big-time Democrat, Barack Obama. But no. When Obama spoke, Burke wasn’t on stage.

It didn’t take long for the Walker campaign to note and try to make hay out of her MIA status. Via rightwisconsin.com:

With Mary Burke doing the Obama-two step on Labor Day, Gov. Walker and his campaign took the opportunity to remind voters that while Burke is afraid to embrace the president publicly she holds many of the same views on politics and policy.

On Friday, Walker’s campaign reminded voters that Mary Burke had given $86,000 in campaign contributions to Barack Obama’s campaign – more than the average family of four earns in one year.

While Mary Burke might be able to keep the press from taking pictures of her and President Barack Obama together this weekend, she can’t keep the public from knowing that she gave more money to the president than the typical Wisconsin family of four earns in an entire year. Burke’s most recent donation came in the form of a lump sum payment of $73,300 to the Obama Victory Fund in 2012.

Recent polling shows the Walker-Burke race to be a virtual tie, which might help explain Mary Burke’s reluctance to be associated with a president whose public approval continues to drop. Via CNN:

The latest Marquette University poll released Wednesday, showed Burke at 48.6% to Walker’s 46.5% among likely voters. Among registered voters, Walker received support from 47.5% of respondents to Burke’s 44.1%. Both results are within the margin of error.

The August poll is in line with other independent polls that show the Walker-Burke race especially close.